The present invention is directed to systems for thermal printing which systems involve the controlled directing of a heated gas against a thermally responsive record medium.
The following list of patents attempts to set forth the state of the prior art:
1,765,448 3,177,800 3,312,979 1,770,493 3,179,042 3,409,904 2,100,204 3,179,946 3,495,070 3,063,050 3,187,669 3,545,374 3,681,778.
The device disclosed in U.S. Pat. No. 1,765,448 entitled "Recorder For Facsimile Systems", by R. H. Ranger, utilizes a heating tube to heat a flow of gas and a shutter positioned at the open end of the heating tube to modulate the heated gas flow as a function of the vibrations associated with a telephone receiver. The modulated hot gas is then directed to a thermally sensitive recording medium to provide a visual record.
In U.S. Pat. No. 1,770,493, entitled "Method And Apparatus for Pyro-Recording", by R. H. Ranger, a similar device is shown wherein the heated gas from the heating tube is modulated by a blast of cold air.
The system disclosed in U.S. Pat. No. 2,100,204 entitled "Facsimile System", by H. Shore, utilizes the shutter arrangement, of the general type, shown in the above referenced U.S. Pat. No. 1,765,448. In combination with this shutter arrangement there is employed multiple heaters which are positioned along the flow path of a vaporized ink to reduce condensation. A reduction in the condensation of the ink vapors permits the use of higher pressures on the ink flow and a greater density of ink. Both of which result in a clearer and darker recorded image.
The device of U.S. Pat. No. 3,179,042, entitled "Sudden Steam Printer" by M. Naiman, utilizes a matrix comprised of individual print means each of which consists of a pair of electrodes immersed in an ink. Application of a voltage to the electrodes causes a current to flow through the ink, which current heats the ink and causes part of the ink to vaporize. The vaporized ink creates a pressure on the ink directly above it, forcing the ink droplets onto a recording medium.
In U.S. Pat. No. 3,409,904, entitled "Printer Having Piezoelectric Crystal Printing Means" by K. Maiershofer, an impact hammer is used to make marks on a pressure sensitive record medium. The hammer is formed from a piezoelectric crystal using a bender bimorph configuration. A potential applied to the crystal causes the crystal to bend and impact a hammer head against a pressure sensitive recording medium.
The device of U.S. Pat. No. 3,545,374, entitled "High-Speed Printer Employing A Gas Discharge Matrix" by C. D. Hendricks, Jr., is comprised of an insulating material having a number of perforations within which are positioned inner electrodes. The inner electrodes are used to initiate ionization of the gas within the perforations in response to an electrical signal. One end of each perforation is closed which results in the ionized gas exploding from the perforations at the open end to impinge upon a record medium that is placed in proximity to the open ends.
From the foregoing descriptions of prior art devices it can be seen that there exists a need for a simple inexpensive thermal type printer system that can respond quickly to digital type signals and provide a permanent record of the response. The systems of the present invention attempt to fill that need.